\Ni"si\, conj. [L.]
Unless; if not.
Note: In legal proceedings, this word is used to indicate
      that any order, etc., shall take effect at a given
      time, unless before that time the order, etc., in
      modified, or something else is done to prevent its
      taking effect. Continuance nisi is a conditional
      continuance of the case till the next term of the
      court, unless otherwise disposed of in the mean time.
{Nisi prius} (Law), unless before; -- a phrase applied to
   terms of court, held generally by a single judge, with a
   jury, for the trial of civil causes. The term originated
   in a legal fiction. An issue of fact being made up, it is,
   according to the English practice, appointed by the entry
   on the record, or written proceedings, to be tried by a
   jury from the county of which the proceedings are dated,
   at Westminster, unless before the day appointed (nisi
   prius) the judges shall have come to the county in
   question (which they always do) and there try the cause.
   See {In banc}, under {Banc}.